Detailed functional morphological investigations of Mekong River hydrobiid snails will be undertaken to delineate their phylogenies, particularly where phylogeny pertains to the transmission of human Mekong schistosomiasis. Emphasis will be placed on Lithoglyphopsis aperta found naturally infected at Khong Island, Laos. It is emphasized that nothing is known of the anatomy, biology or genetic relationships between any of the some 80 hydrobiid species of the Mekong River. Anatomical studies are essential to establish base line biological data, establish which taxa are related to L. aperta and thus are potential intermediate hosts of Mekong shcistosomiasis, and to assess the relationship, if any, to the hydrobiid Oncomelania which transmits S. japonicum in China, Philippines, etc. Taxa found phylogenetically closely realted to Lithoglyphopsis or Oncomelania will be studied by the Smithsomian-USAID team (see below) for susceptibility to Mekong schistosomiasis and S. japonicum. Implementation of this proposal would enable supplementation to the Smithsonian-USAID project on the "Ecology of Water-Borne Disease of the Mekong" in that thousands of specimens collected from the Mekong could be sorted and identified using the Academy of Natural Sciences' unique reference collections and library facilities. Profiles of molluscan fauna at critical places in the Mekong will be made where taxa are correlated with micro-niches. The water chemistry of the micro-habitats will be done by the Smithsomian team. Together, the species profiles and assessment of potential for transmitting schistosomiasis will enable knowledgeable advice to the Mekong Committee as related to creation of super dams, river management, and the future of public health.